Question

An element A (atomic weight = $100$ amu) having bcc structure has unit cell edge length of $400$ pm. Calculate the density (in g/cc) of A?

• A. $5.188$
• B. $7.188$
• C. $4.144$
• D. $10.144$

Answer 1

Answer: (A)

$5.188$

Density(g/mol)= $\frac{Z.M}{a^3.N_A}$ , where

Z: number of atoms per unit cell = 2 for BCC

M: Atomic Weight = 100 amu

a: edge cell length in cm = 400 x ${10}^{-10}$ cm

$N_A$: Avogadro Number = $6.023\times {10}^{23}$

Therefore, Density = $\frac{2\times 100}{400\times {10}^{-10}\times 6.023\times {10}^{23}}$

= 5.188 g/mol

Hence, options A is correct.